The invention relates generally to the field of digital power monitoring and control. More specifically the invention relates to a power monitoring and control apparatus incorporating an application specific integrated circuit.
The field of digital power monitoring and control includes such devices as energy/power meters, protective relays, Programmable Logic Controllers (“PLC's”), Remote Terminal Units (“RTUs”), fault recorders, power quality monitors, etc. Generally these devices are referred to as Intelligent Electronic Devices (“IEDs”). Due to the continuing pressure to reduce the cost of electrical installations, the different types of IEDs continue to incorporate and integrate the features of one another. For instance, it is common to find digital power meters incorporating features of fault recorders and power quality monitors. In addition protective relays are incorporating more and more power meter functionality.
A typical digital power meter is described in U.S. Pat. No. 6,185,508 to Van Doom et al. entitled “Power Meter for Determining Parameters of Multiphase Power Lines.” This power meter contains a number of circuit elements including a processor, memory, analog and digital interface circuitry, communications circuitry, display circuitry, etc. The device is highly programmable as it contains both non-volatile RAM and flash memory allowing both the user and the manufacturer the ability to configure the device to perform different functions.
A typical protective relay is described in U.S. Pat. No. 5,793,595 to Schweitzer et al. entitled “Multi-Application Relay for Power Systems.” This device includes similar circuitry as a digital power meter although the software and application are different.
Application Specific Integrated Circuits (“ASICs”) capable of calculating power parameters such as rns voltage, rns current and power are available. Such ASICS may also be capable of generating energy signals representative of the calculated energy parameters. Typical devices are described in U.S. Pat. No. 5,862,069 to Nestler (“Four Quadrant Multiplying Apparatus and Method”), U.S. Pat. No. 6,278,392 to Nestler (“Gain Adjustable Sigma Delta Modulator System”) and U.S. Pat. No. 6,417,792 to King et al. (“Single Phase Bi-Directional Electrical Measurement Systems and Methods Using ADCs”). These devices are typically inflexible as to the functions they perform and are often not practical for use in advanced programmable IEDs.